1. Field of the Invention:
The present invention relates to a thread cutting bit made of a carbide cutting material with a bearing face and a cover face essentially parallel to it, as well as with at least one face edge or cutting corner which, depending on the type of thread being cut, forms a profiled cutting tip, with cutting edges. Above the cutting faces is located a chip forming element with flanks, of which, in the manner of the steep walls of a spur or plateau, maintain a distance from the neighboring cutting edges that contain, enclose or includes the associated cutting faces. The term "spur" is used to provide a graphic description of the configuration of the chip forming element between the cutting faces located on a face edge or cutting corner. According to the "Brockhaus Enzyklopadie" [Brockhaus Encyclopedia] 1993, Volume 19, the geological feature called a "spur" is defined as a "projecting land form, generally steep-walled, in particular at the intersection between two deep valleys that intersect at an acute angle." A triangular thread cutting bit of the known art with three geometrically identical faces and having the generic characteristics as indicated above is disclosed in WO 95/07159.
2. Background Information
The purpose of the thread cutting bit of the known art is to control the shaping of the chip by means of the geometric configuration of the respective cutting face that is in the engaged position, so that shorter chips are formed. The purpose of this type of operation is to prevent a clogging of the chip flute, which is hazardous for the operator. Consequently, this thread-cutting bit of the known art can also be used in mass-production operations where it is not constantly monitored by operating personnel.
The invention is based on the knowledge that when threads are being cut using conventional cutting bits, the surface of a cutting face is provided with a chip shaping stage that is shaped at an angle. Generally, such cutting bits are perforated, disposable bits having a triangular shape with a cutting face shaped onto each corner in the form of a thread profile tooth. When threads are being cut with such cutting bits, because the cutting or feed parameters can change either very little or not at all, very stable ribbon or mingled-up chips with a V-shaped cross section are formed, which have a very disruptive effect on CNC drilling machines that are installed in very tight spaces, as well as on the fabrication process as a whole.